Semiotic class normalization

ABSTRACT

A language processing system for text normalization of an input string of a semiotic class. In an aspect, a method includes receiving an input string; accessing, for a semiotic class of non-standard words, a language universal covering grammar for a plurality of languages that generates, for each language of the plurality of languages, one or more sequences of word-level components for each instance of the semiotic class in the language; for each of the plurality of languages, accessing a lexical map specific to the language and that maps each sequence of word-level components for each instance of the semiotic class in the language verbalizations in the language; generating, from the language universal grammar and the lexical maps, a lattice of possible verbalizations of the input string; and selecting one of the possible verbalizations as a selected verbalization for the input string.

BACKGROUND

This specification relates to speech and language recognition andunderstanding systems.

Speech recognizers and synthesizers require systems to convertnon-standard words, such as numbers (e.g., 97), dates (e.g., 3/23),times (e.g., 8:50 pm), currency expressions (e.g., $1.50), measurephrases (e.g., 10 kg), abbreviations (e.g., St.) and the like topronounceable versions (ninety-seven, March twenty-third, etc.). Such apronounceable version expressed in terms of ordinary words is referredto as a “verbalization.”

For many languages, the non-standard words may be grouped into classes,such as cardinal numbers, dates, times, and so on. Each such class isreferred to as a semiotic class, e.g., the semiotic classes of cardinalnumbers, dates, times, etc.

The process of converting instances of semiotic classes toverbalizations is referred to as text normalization. This is largelyaccomplished by hand-built grammars written by native speaker linguists,and require many man-hours for each language. The process of training orwriting a selector for selecting a verbalization is also labor intensiveand requires a large amount of training data, which, in turn, has acommensurate computer resource requirement.

SUMMARY

In general, one innovative aspect of the subject matter described inthis specification can be embodied in methods that include the actionsof receiving an input string; accessing, for a semiotic class ofnon-standard words, a language universal covering grammar for aplurality of languages that generates, for each language of theplurality of languages, one or more sequences of word-level componentsfor each instance of the semiotic class in the language; for each of theplurality of languages, accessing a lexical map specific to the languageand that maps each sequence of word-level components for each instanceof the semiotic class in the language verbalizations in the language;generating, from the language universal grammar and the lexical maps, alattice of possible verbalizations of the input string; and selectingone of the possible verbalizations as a selected verbalization for theinput string. Other embodiments of this aspect include correspondingsystems, apparatus, and computer programs, configured to perform theactions of the methods, encoded on computer storage devices.

Particular embodiments of the subject matter described in thisspecification can be implemented so as to realize one or more of thefollowing advantages. The process of inducing grammars and selecting amost appropriate verbalization for an input string can be accomplishedwith minimal knowledge about the languages that are served and arelatively small amount of parallel data when compared to existingsystems. This yields a technological improvement in the technology areaof language processing by reducing development time and processingresources required for building a semiotic class text normalizationsystem. The process also reduces the amount of trainers′/administrators'linguistic expertise required in that all that is needed is alinguistically aware speaker of a language, rather than someone who hasexperience at grammar development.

The details of one or more embodiments of the subject matter describedin this specification are set forth in the accompanying drawings and thedescription below. Other features, aspects, and advantages of thesubject matter will become apparent from the description, the drawings,and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of an environment in which an input string ofa semiotic class is processed to determine a verbalization.

FIG. 2 is a flow diagram of an example process for determining averbalization from an input string of a semiotic class.

FIG. 3 is a block diagram of a training system for the verbalizationselector.

FIG. 4 is flow diagram of an example process training the verbalizationselector.

Like reference numbers and designations in the various drawings indicatelike elements.

DETAILED DESCRIPTION

FIG. 1 is a block diagram of an environment 100 in which an input stringof a semiotic class is processed to determine a verbalization. Acomputer network 102, such as a local area network (LAN), wide areanetwork (WAN), the Internet, or a combination thereof, provides for datacommunication between electronic devices and systems. Examples of suchelectronic device and systems include web sites 104 and user devices106.

A website 104 includes one or more resources 105 associated with adomain name and hosted by one or more servers. An example website is acollection of web pages formatted in hypertext markup language (HTML)that can contain text, images, multimedia content, and programmingelements, such as scripts. Each website 104 is maintained by a contentpublisher, which is an entity that controls, manages and/or owns thewebsite 104. A resource 105 is any data that can be provided by thewebsite 104 over the network 102 and that is associated with a resourceaddress.

Some or all of the resources 105 may be indexed in resource corpora 110.The resource corpora 110 may be created and maintained by a searchsystem (not shown), or by some other system.

A user device 106 is an electronic device that is under the control of auser and is capable of requesting and receiving resources over thenetwork 102, establishing communication channels, e.g., voicecommunications, with other user devices 106, and also capable ofperforming other actions. Example user devices 106 include personalcomputers, mobile communication devices, and other devices that can sendand receive data over the network 102.

The resource corpora 110 and resources 105 may be accessed by a languageprocessing system 120. The language processing system 120 may perform avariety of functions and services, such as text-to-speech recognition,translations, and the like. One of the capabilities of languageprocessing system 120 is text normalization for input strings ofsemiotic classes.

In the example implementation shown in FIG. 1, the language processingsystem 120 includes a verbalization generator 122 and a verbalizationselector 124. At a high level, the verbalization generator 122 receivesan input string w and accesses a covering grammar stored in the coveringgrammar data 130 and language specific lexical maps stored in thelanguage specific lexical map data 132. The verbalization generator 122generates a collection of possible verbalizations Hw for the inputstring w, and, using a verbalization selector 124, selects anappropriate verbalization v for the input string w.

The language processing system 120 may be implemented in one or morecomputers in data communication with each other. Operation of thelanguage processing system 120 is described in more detail withreference to FIG. 2, which is a flow diagram of an example process 200for determining a verbalization from an input string of a semioticclass.

The process 200 receives an input string (202). For example, theverbalization generator 122 may receive an input string w. The stringmay be processed by many language processes in parallel, such as namerecognition, entity identification, command processing, and the like.Here the verbalization generator 122 and the verbalization 124 performtext normalization for semiotic classes. Thus, assume that the inputstring w includes text belonging to a semiotic class.

The process 200 accesses, for a semiotic class of non-standard words, alanguage universal covering grammar for a plurality of languages thatgenerates, for each language of the plurality of languages, one or moresequences of word-level components for each instance of the semioticclass in the language (204). The language-universal covering grammar Ggenerates possible ways that a language might verbalize a semiotic classfor multiple languages. For example, the language universal coveringgrammar G for the cardinal number semiotic class may generate, for theinput string 97, the following word level components, where each digitstring such as “90” or “80” is understood to stand for a word or wordsof the target language:

90 7 (English)

7 90 (German)

80 10 7 (Georgian)

4 20 10 7 (French)

. . .

The language-universal covering grammar G is designed to cover thereasonable (e.g., most common or most likely) ways in which a givenlanguage might verbalize a given expression. For example, the coveringgrammar G takes into account that a language might express 97 as acombination of a word for “90” followed by a word for “7,” as inEnglish; or a word for “80” followed by a word for “10” followed by aword for “7” as in Georgian, etc.

For each semiotic class, the covering grammar G incorporates rules thatwill map the input string to the word-level components in the languages.For example, for the example cardinal number semiotic class describedabove, the covering grammar G may include factorization rules that areconsistent with the spoken form of the cardinal number in each language.Thus, for a given input number, the grammar G outputs a sequence of twoor more second numbers that are a language specific factorization of thefirst number. For example, in English, 97000 is factored as 90 7 1000.However, in Standard French, for example, there is no simplex numbername for ‘90’; instead this is realized as quatre-vingt-dix “four twentyten”, and thus 97000 (quatre-vingt-dix-sept mille) is factored as 4 2010 7 1000. By way of another example, for the semiotic class of weightmeasurements, the non-standard word “kg” in English may be mapped to“kilogram” and “kilos.”

The process 200, for each of the languages, accesses a lexical map Lspecific to the language and that maps each sequence of word-levelcomponents for each instance of the semiotic class in the languageverbalizations in the language (204). Each language specific lexical mapL generates possible pronunciations of the word-level components ofnon-standard words. For example, in English, the a lexical map L forcardinal numbers maps 10 to ten, 20 to twenty, and so on. Likewise, forthe semiotic class of currency, the non-standard word $ is mapped todollar and dollars, etc.

The process 200 generates, from the language universal grammar and thelexical maps, a lattice of possible verbalizations v of the input string(208). For example, for the input string 97, the verbalization generator122, using the covering grammar G, generates 90 7 for the English wordlevel components of the semiotic class of cardinal numbers, and 4 20 107 for the standard French word level components. Thereafter, theverbalization generator 122, using the language specific lexical maps L,generates “ninety seven” for English and “quatre vingt dix sept” forFrench.

In implementations for which G and L are both finite state transducers,then the verbalization generator 122 generates Hw=π_(o)(w o G o L),where Hw is a lattice of all possible verbalizations for somenon-standard input string w, and π_(o) is an output projection that is afinite automaton that accepts a stringy if and only if there exists astring x such that Hw(x)→y.

The process 200 selects one of the possible verbalizations as a selectedverbalization for the input string (210). A variety of appropriateselection processes can be used. For example, in some implementations,the verbalization selector 124 may have access to grammatical rulesetsfor each language. Each grammatical ruleset is then applied to eachpossible verbalization. Each possible verbalization that does not complywith a ruleset may be filtered from being selected as a verbalization.For example, in English, for the class of cardinal numbers, the possibleverbalization “four twenty ten seven” would not comply with agrammatical rule set for verbalization of the input string “97.”However, for the grammatical rule set of standard French, the possibleverbalization “quatre vingt dix sept” would comply with a grammaticalrule set for the verbalization of “97.”

Another selection process is a scoring process function that generates averbalization score for each possible verbalization. The possibleverbalization with a “best” verbalization score is then selected as theselected verbalization for the input string. For example, theverbalization selector 124 may be implemented as a weighted finite stateacceptor that receives each possible verbalization and generates a scorefor only each accepted possible verbalization. The verbalizationselector 124 is encoded with a language model specific to the semioticclass. The verbalization v that is selected for the input string w isthe one with a highest verbalization score.

Another scoring model that may be implemented in the verbalizationselector 124 may be based on a supervised sequence model, in which casev is the highest-scoring path through Hw. In that case, parallel data ofsequences of non-standard words and the corresponding verbalizations inthe target language are used to train the verbalization selector 124. Inone implementation, the scoring function of the verbalization selector124 is a Maximum Entity (MaxEnt) ranker that is trained using paralleldata. For example, for the semiotic class of cardinal numbers, theverbalization selector is trained using written data of text thatincludes numbers written as digit sequences and spoken data in the formof text that contains the words that a speaker would actually utter whenreading the digit sequences.

This is illustrated in FIG. 3, which is a block diagram of a trainingsystem for the verbalization selector 124. The training process isillustrated by the flow diagram of the process 400 of FIG. 4.

The process 400 accesses parallel written data and spoken data (402).For example, the machine learner system 140 process receives the writtendata and spoken data {w′}, {v′}. The process 400 then trains the scoringmodel to learn preferred lattice outputs for given instances of thesemiotic class in each language (404).

In implementations in which finite state transducers are used, thescoring model can be trained without any true parallel data. This is dueto the property that finite state transducers are invertible: atransducer that maps from digit sequences to number names can beinverted, resulting in a transducer that maps number names to digitsequences. Utilizing this property, a system can map from spoken towritten expression form rather than from written expression form tospoken form, e.g., the input “twenty-three” produces the output “23.”Accordingly, spoken data can be used to produce a set of potentialwritten forms. The scoring model is then trained with the synthetictraining data as describe above.

More generally, the system may be used to consider implicitly allpossible written forms and the spoken forms that might be generated fromthem. Consider a verbalization transducer V and its inverse V⁻¹. Thesystem can produce a “round trip” set of verbalizations such that if theoriginal spoken form was y, then the set of possible verbalizations isgiven as π_(o)[/y o V⁻¹ o V].

These potential other verbalizations are then be used to train aclassifier that will prefer the true verbalization over the otherpotential verbalizations.

In various implementations, operations that are performed “in responseto” or “as a consequence of” another operation (e.g., a determination oran identification) are not performed if the prior operation isunsuccessful (e.g., if the determination was not performed). Operationsthat are performed “automatically” are operations that are performedwithout user intervention (e.g., intervening user input). Features inthis document that are described with conditional language may describeimplementations that are optional. In some examples, “transmitting” froma first device to a second device includes the first device placing datainto a network for receipt by the second device, but may not include thesecond device receiving the data. Conversely, “receiving” from a firstdevice may include receiving the data from a network, but may notinclude the first device transmitting the data.

Embodiments of the subject matter and the operations described in thisspecification can be implemented in digital electronic circuitry, or incomputer software, firmware, or hardware, including the structuresdisclosed in this specification and their structural equivalents, or incombinations of one or more of them. Embodiments of the subject matterdescribed in this specification can be implemented as one or morecomputer programs, i.e., one or more modules of computer programinstructions, encoded on computer storage medium for execution by, or tocontrol the operation of, data processing apparatus. Alternatively or inaddition, the program instructions can be encoded on anartificially-generated propagated signal, e.g., a machine-generatedelectrical, optical, or electromagnetic signal that is generated toencode information for transmission to suitable receiver apparatus forexecution by a data processing apparatus. A computer storage medium canbe, or be included in, a computer-readable storage device, acomputer-readable storage substrate, a random or serial access memoryarray or device, or a combination of one or more of them. Moreover,while a computer storage medium is not a propagated signal, a computerstorage medium can be a source or destination of computer programinstructions encoded in an artificially-generated propagated signal. Thecomputer storage medium can also be, or be included in, one or moreseparate physical components or media (e.g., multiple CDs, disks, orother storage devices).

The operations described in this specification can be implemented asoperations performed by a data processing apparatus on data stored onone or more computer-readable storage devices or received from othersources.

The term “data processing apparatus” encompasses all kinds of apparatus,devices, and machines for processing data, including by way of example aprogrammable processor, a computer, a system on a chip, or multipleones, or combinations, of the foregoing The apparatus can includespecial purpose logic circuitry, e.g., an FPGA (field programmable gatearray) or an ASIC (application-specific integrated circuit). Theapparatus can also include, in addition to hardware, code that createsan execution environment for the computer program in question, e.g.,code that constitutes processor firmware, a protocol stack, a databasemanagement system, an operating system, a cross-platform runtimeenvironment, a virtual machine, or a combination of one or more of them.The apparatus and execution environment can realize various differentcomputing model infrastructures, such as web services, distributedcomputing and grid computing infrastructures.

A computer program (also known as a program, software, softwareapplication, script, or code) can be written in any form of programminglanguage, including compiled or interpreted languages, declarative orprocedural languages, and it can be deployed in any form, including as astand-alone program or as a module, component, subroutine, object, orother unit suitable for use in a computing environment. A computerprogram may, but need not, correspond to a file in a file system. Aprogram can be stored in a portion of a file that holds other programsor data (e.g., one or more scripts stored in a markup languagedocument), in a single file dedicated to the program in question, or inmultiple coordinated files (e.g., files that store one or more modules,sub-programs, or portions of code). A computer program can be deployedto be executed on one computer or on multiple computers that are locatedat one site or distributed across multiple sites and interconnected by acommunication network.

The processes and logic flows described in this specification can beperformed by one or more programmable processors executing one or morecomputer programs to perform actions by operating on input data andgenerating output. The processes and logic flows can also be performedby, and apparatus can also be implemented as, special purpose logiccircuitry, e.g., an FPGA (field programmable gate array) or an ASIC(application-specific integrated circuit).

Processors suitable for the execution of a computer program include, byway of example, both general and special purpose microprocessors, andany one or more processors of any kind of digital computer. Generally, aprocessor will receive instructions and data from a read-only memory ora random access memory or both. The essential elements of a computer area processor for performing actions in accordance with instructions andone or more memory devices for storing instructions and data. Generally,a computer will also include, or be operatively coupled to receive datafrom or transfer data to, or both, one or more mass storage devices forstoring data, e.g., magnetic, magneto-optical disks, or optical disks.However, a computer need not have such devices. Moreover, a computer canbe embedded in another device, e.g., a mobile telephone, a personaldigital assistant (PDA), a mobile audio or video player, a game console,a Global Positioning System (GPS) receiver, or a portable storage device(e.g., a universal serial bus (USB) flash drive), to name just a few.Devices suitable for storing computer program instructions and datainclude all forms of non-volatile memory, media and memory devices,including by way of example semiconductor memory devices, e.g., EPROM,EEPROM, and flash memory devices; magnetic disks, e.g., internal harddisks or removable disks; magneto-optical disks; and CD-ROM and DVD-ROMdisks. The processor and the memory can be supplemented by, orincorporated in, special purpose logic circuitry.

To provide for interaction with a user, embodiments of the subjectmatter described in this specification can be implemented on a computerhaving a display device, e.g., a CRT (cathode ray tube) or LCD (liquidcrystal display) monitor, for displaying information to the user and akeyboard and a pointing device, e.g., a mouse or a trackball, by whichthe user can provide input to the computer. Other kinds of devices canbe used to provide for interaction with a user as well; for example,feedback provided to the user can be any form of sensory feedback, e.g.,visual feedback, auditory feedback, or tactile feedback; and input fromthe user can be received in any form, including acoustic, speech, ortactile input. In addition, a computer can interact with a user bysending documents to and receiving documents from a device that is usedby the user; for example, by sending web pages to a web browser on auser's user device in response to requests received from the webbrowser.

Embodiments of the subject matter described in this specification can beimplemented in a computing system that includes a back-end component,e.g., as a data server, or that includes a middleware component, e.g.,an application server, or that includes a front-end component, e.g., auser computer having a graphical user interface or a Web browser throughwhich a user can interact with an implementation of the subject matterdescribed in this specification, or any combination of one or more suchback-end, middleware, or front-end components. The components of thesystem can be interconnected by any form or medium of digital datacommunication, e.g., a communication network. Examples of communicationnetworks include a local area network (“LAN”) and a wide area network(“WAN”), an inter-network (e.g., the Internet), and peer-to-peernetworks (e.g., ad hoc peer-to-peer networks).

The computing system can include users and servers. A user and serverare generally remote from each other and typically interact through acommunication network. The relationship of user and server arises byvirtue of computer programs running on the respective computers andhaving a user-server relationship to each other. In some embodiments, aserver transmits data (e.g., an HTML page) to a user device (e.g., forpurposes of displaying data to and receiving user input from a userinteracting with the user device). Data generated at the user device(e.g., a result of the user interaction) can be received from the userdevice at the server.

While this specification contains many specific implementation details,these should not be construed as limitations on the scope of anyinventions or of what may be claimed, but rather as descriptions offeatures specific to particular embodiments of particular inventions.Certain features that are described in this specification in the contextof separate embodiments can also be implemented in combination in asingle embodiment. Conversely, various features that are described inthe context of a single embodiment can also be implemented in multipleembodiments separately or in any suitable subcombination. Moreover,although features may be described above as acting in certaincombinations and even initially claimed as such, one or more featuresfrom a claimed combination can in some cases be excised from thecombination, and the claimed combination may be directed to asubcombination or variation of a subcombination.

Similarly, while operations are depicted in the drawings in a particularorder, this should not be understood as requiring that such operationsbe performed in the particular order shown or in sequential order, orthat all illustrated operations be performed, to achieve desirableresults. In certain circumstances, multitasking and parallel processingmay be advantageous. Moreover, the separation of various systemcomponents in the embodiments described above should not be understoodas requiring such separation in all embodiments, and it should beunderstood that the described program components and systems cangenerally be integrated together in a single software product orpackaged into multiple software products.

Thus, particular embodiments of the subject matter have been described.Other embodiments are within the scope of the following claims. In somecases, the actions recited in the claims can be performed in a differentorder and still achieve desirable results. In addition, the processesdepicted in the accompanying figures do not necessarily require theparticular order shown, or sequential order, to achieve desirableresults. In certain implementations, multitasking and parallelprocessing may be advantageous.

What is claimed is:
 1. A system, comprising: a data processingapparatus; and a non-transitory computer readable storage medium in datacommunication with the data processing apparatus storing instructionsexecutable by the data processing apparatus and that upon such executioncauses the data processing apparatus to perform operations comprising:receiving an input string; accessing, for a semiotic class ofnon-standard words, a language universal covering grammar for aplurality of languages that generates, for each language of theplurality of languages, one or more sequences of word-level componentsfor each instance of a member of the semiotic class in the language; foreach of the plurality of languages, accessing a lexical map specific tothe language and that maps each sequence of word-level components foreach instance of a member of the semiotic class in the language toverbalizations in the language; generating, from the language universalgrammar and the lexical maps, a lattice of possible verbalizations ofthe input string; and selecting one of the possible verbalizations as aselected verbalization for the input string.
 2. The system of claim 1,wherein selecting one of the possible verbalizations as a selectedverbalization for the input string comprises: generating, for eachpossible verbalization of the input string, a verbalization scoreaccording to a scoring function; and selecting one of the possibleverbalization as the selected verbalization for the input string basedon the respective verbalization scores.
 3. The system of claim 2,wherein the scoring function comprises, for each language, a weightedfinite state acceptor that receives each possible verbalization andgenerates a score for only each possible verbalization accepted by theweighted finite state acceptor.
 4. The system of claim 2, wherein thescoring function comprises, for each language, a scoring model that istrained using written expressions of numbers and spoken words for eachwritten expression.
 5. The system of claim 4, wherein the writtenexpressions of numbers are collected from a corpus of documents.
 6. Thesystem of claim 4, wherein for each language, the written expressions ofnumbers are generated from spoken words that are applied as in input toan inversion of the lexical map and the language universal grammar. 7.The system of claim 1, wherein selecting one of the possibleverbalizations as a selected verbalization for the input stringcomprises: applying to each possible verbalization of the input string,a grammatical ruleset for the language of the possible verbalization;and selecting one of the possible verbalizations as a selectedverbalization for the input string based on the selected verbalizationsatisfying the grammatical ruleset that was applied to it.
 8. The systemof claim 1, wherein the semiotic class is one of a cardinal numberclass, a date class, and a currency class.
 9. The system of claim 1,wherein the semiotic class is a cardinal number class, and the languageuniversal covering grammar receives as input a first number andgenerates as output a sequence of two or more second numbers that are alanguage specific factorization of the first number.
 10. The system ofclaim 9, wherein each lexical map receives as input one or more of thefirst number and the two or more second numbers that are a languagespecific factorization of the first number and generates as outputpossible verbalizations of the input to the lexical map.
 11. The systemof claim 9, wherein language universal covering grammar and each lexicalmap are finite state transducers.
 12. A non-transitory computer readablestorage medium storing instructions executable by a data processingapparatus and that upon such execution causes the data processingapparatus to perform operations comprising: receiving an input string;accessing, for a semiotic class of non-standard words, a languageuniversal covering grammar for a plurality of languages that generates,for each language of the plurality of languages, one or more sequencesof word-level components for each instance of a member of the semioticclass in the language; for each of the plurality of languages, accessinga lexical map specific to the language and that maps each sequence ofword-level components for each instance of a member of the semioticclass in the language to verbalizations in the language; generating,from the language universal grammar and the lexical maps, a lattice ofpossible verbalizations of the input string; and selecting one of thepossible verbalizations as a selected verbalization for the inputstring.
 13. A computer implemented method, comprising: receiving aninput string; accessing, by a computer system and for a semiotic classof non-standard words, a language universal covering grammar for aplurality of languages that generates, for each language of theplurality of languages, one or more sequences of word-level componentsfor each instance of a member of the semiotic class in the language; foreach of the plurality of languages, accessing, by the computer system, alexical map specific to the language and that maps each sequence ofword-level components for each instance of a member of the semioticclass in the language to verbalizations in the language; generating, bythe computer system and from the language universal grammar and thelexical maps, a lattice of possible verbalizations of the input string;and selecting, by the computer system, one of the possibleverbalizations as a selected verbalization for the input string.